Central British Columbia Research Articles

Past Groundwater Drought in the North American Cordillera

AbstractGroundwater level records in North America are relatively short (<60 years), preventing long‐term analysis of historical changes in groundwater levels associated with drought. In this study, tree ring widths are used to reconstruct groundwater levels in three regions in the North American Cordillera: Central British Columbia (BC), Canada, the Southern Interior Region of BC, and the San Luis Valley in Colorado, USA. Periods with severe drought conditions, identified using regime shift and threshold analyses were: 1890–1900 and 1950–1970 in Colorado, around 1920–1940 in the BC Interior, and 1935–1945 in Central BC. The groundwater level reconstructions are correlated with several climate indices and have similar regime shifts as identified in streamflow and drought records. The groundwater level reconstructions are strongly related to winter snowpack, suggesting that the observed trend of declining snowpack in recent years may lead to declining groundwater availability in these regions.

Spatial scale of stand-replacing forest disturbance influences the amplitude of snowshoe hare population fluctuations in boreal forests of northwest Canada

The natural disturbance model for ecosystem management of timber harvesting promotes the emulation of natural disturbance regimes in the patterns of tree removal. Wildfire is a prominent natural disturbance in boreal forests of western Canada, frequently removing most of the tree canopy from patches of 500–10,000 ha in stand-replacing events. However, fire suppression, coupled with a spatial pattern of timber harvesting dominated by small patch cuts of 10–160 ha, have changed the spatial scale of younger stands away from scales within which boreal organisms evolved. In two regions (Sub-Boreal Spruce biogeoclimatic zone of central British Columbia and Liard Basin of southeast Yukon), we tested the hypothesis that different spatial scales of stand-replacing forest disturbance (wildfire and timber harvesting) result in different amplitudes of change in abundance of snowshoe hare, a keystone boreal forest mammal for which mid-seral stand conditions provide optimal habitat. Landscapes with large patches (>2000 ha) of mid-seral forest following stand-replacing disturbance supported consistently and often significantly more hares, with wider amplitude in cyclic fluctuation, than small patches (20–200 ha) of mid-seral habitat and than mature forest landscapes. Densities of hares high enough to support reproduction by Canada lynx (a specialist hare predator) only occurred in landscapes disturbed at the scale of a moderate to large-sized wildfire (1000 – 10,000 ha). Landscapes unaffected by stand-replacing disturbance for at least 80 years (i.e. mature forests) supported very few hares and without cyclic fluctuations. We recommend that the recent pattern of cutting dominated by small patches (20–200 ha) be shifted to include many larger patches (2000–5000 ha). This can happen with incremental, contiguous patch cutting over a period of years short enough that the completed patch will supply high quality, mid-seral habitat for at least the period of one hare cycle (10 y). In designing relatively large patches, mature green tree retention would be desirable for various values, but would be best as small stands of mature forest dispersed within large patch cuts, similar to the legacy of fire. Silviculture (reforestation and stand tending) should create and sustain a mix of conifer and deciduous regeneration in the mid-seral stands. Emulating spatial patterns of stand-replacing natural disturbance appears necessary to sustain snowshoe hare cycles when most fires are suppressed in intensively managed western Canadian boreal forests.

Delineating wildfire burns and regrowth using satellite imagery to assess moose (Alces alces) spatial responses to burns

AbstractClimate change is predicted to increase the frequency and size of wildfires. Wildfire burns can influence wildlife space use, but prior to understanding the relationship between wildlife and burns, the extent of wildfires and the regrowth of burned areas must be determined. We used remotely sensed, multispectral satellite imagery to calculate differenced normalized burn ratios (NBRs) to define areas burned by wildfire and assess temporal trends in burn frequency and extent in central British Columbia. We then used NBRs as an index of vegetation regrowth to model regrowth trajectories within burns. Next, we examined spatial responses to burns by a moose (Alces alces) population that recently declined in abundance. We utilized locations used by and available to collared moose to determine spatial responses as a function of years since wildfire and vegetation regrowth. We also assessed functional responses to burns by moose, dependent upon the proportion of burned areas available to each individual. We hypothesized that (h1) wildfire burns within our study area increased from 1985 to 2017, (h2) that moose increase their use of burns in comparison with availability as burns age as a result of vegetation regrowth, and (h3) that moose demonstrate functional responses to burns (i.e., selection of burns by individual moose declines as the amount of burned areas increases). We observed that the frequency and extent of burns are increasing within our study area. In contrast to h2, moose in summer and fall decreased the selection of burns as burns aged. We, however, observed that moose responded most positively to locations with intermediate vegetation regrowth (i.e., NBR values), which according to burn regrowth trajectories were most likely to be achieved 13 or more years post‐wildfire; given that most burns within our study area were ≤13 years of age, we predict that the use of burns will likely increase as vegetation regrows. Moose only selected for burns in fall, and we did not find support for the presence of a functional response. Our research demonstrated the utility of remotely sensed imagery and NBRs to define burn locations and to reveal current and probable future spatial responses to burns by a wildlife population of concern.

Effects of burn severity and postfire salvage logging on carnivore communities in montane forests

Abstract Wildfire and postfire salvage logging are major drivers of forest succession in western North America. Although postfire landscapes support a variety of carnivore species, it is unclear how these animals respond to differing patterns and severities of burning, or to additional landscape change from postfire salvage logging. Open, early-seral habitats created by these disturbances are predicted to benefit generalists such as coyotes (Canis latrans) and weasels (Mustela spp.), but restrict the activity of forest specialists such as Canadaian Lynx (Lynx canadensis) and Pacific Marten (Martes caurina). We used winter track surveys, supplemented with remote cameras, to examine carnivore habitat use in and around large, mixed-severity burns in north-central Washington, United States (burned in 2006), and central British Columbia, Canada (burned in 2010, then partially salvage-logged; some areas reburned in 2017). At 10 to 13 years postfire, marten had similar detection rates across lightly and severely burned areas of the 2006 burn, as did coyotes. Marten selected lightly burned areas of the 2010 burn (6 to 9 years postfire) over higher burn severities, and selected burns over adjacent unburned forests. Weasels selected areas of higher burn severity on both landscapes, while Lynx selected lower burn severities. Weasels and coyotes selected areas with a greater proportion of salvage-logged habitat in the 2010 burn, while marten, lynx, and wolves (Canis lupus) avoided areas with salvage logging. Fishers (Pekania pennanti) showed no clear patterns of selection or avoidance in relation to burn severity or salvage logging. Burn severity strongly influences wildlife activity postfire; lightly burned residual habitats are critical for forest specialists. Postfire salvage logging alters carnivore communities and may hinder species that require structurally complex landscapes.

Magnesite everywhere: Formation of carbonates in the alkaline lakes and playas of the Cariboo Plateau, British Columbia, Canada

The Cariboo Plateau in central British Columbia, Canada, hosts the largest aerial extent of low temperature lacustrine magnesite in the world. Magnesite was the most abundant carbonate mineral in 21 of 33 sampled alkaline lakes and 20 of 22 sampled playas. Calcite, hydromagnesite and very high magnesium calcite (VHMC, also called disordered dolomite) were also found in closed basin alkaline lakes on the plateau. Carbonate mineralogy was strongly associated with lake water geochemistry, particularly total alkalinity. VHMC was the dominant carbonate mineral in lakes with the highest alkalinities (>1000 mEq/kg), magnesite was the dominant carbonate mineral in lakes in the middle range of alkalinities (generally 70 to 800 mEq/kg) and hydromagnesite with minor amounts of magnesite was the phase assemblage in lakes with lower relative alkalinities (<110 mEq/kg). The geochemical trends for the activity of CO32−, Ca2+ and Mg2+ suggest that these constituents in all Cariboo water bodies are controlled by the precipitation of Ca- and/or Mg‑carbonate minerals. The waters are near equilibrium with metastable crystalline Ca‑carbonate and Mg‑carbonate minerals. We hypothesize that carbonates present in the lakes likely formed via non-classical crystallization pathways based on the relationship between aqueous geochemistry and mineralogy and the chemical composition of the Ca-bearing magnesites. Non-classical crystallization offers new models for thinking about magnesite formation in lacustrine environments.

Preliminary discussion on pyrrhotite, gold killer in Wells-Barkerville, British Columbia, Canada

The Wells-Barkerville area of the Cariboo gold mining district is situated within the Quesnel Highlands on the eastern edge of the Interior Plateau in central British Columbia, Canada of the eastern Circum-Pacific volcanicmetallogenic belt. Recorded gold production from the area totals more than 4.0 million ounces, including an estimated 2.7 million ounces from placer mining from 101 creeks and 1.3 million ounces from lode mining. There are five principal types of lode gold deposits in the district; namely, auriferous pyrite replacement, including replacement in limestone and that in calcareous clastic rock; pyrite-quartz vein/veinlet lode gold, including strike vein, diagonal vein, orthogonal vein, and quartz veinlets; basalt-hosted auriferous pyrrhotite-pyrite lode gold; and associated gold in porphyry copper styles. This area is historically a famous gold production area in western Canada, including the initial alluvial gold and later and current lode gold. This original short article uses drilling results to illustrate that pyrrhotite in this area is the killer of gold. Wherever there is pyrrhotite, the gold grade is very poor or even contains no gold. In other words, gold grade is inversely related to pyrrhotite content. Then, the spatial distribution characteristics of the pyrrhotite anomaly zone(s) existing in this area were summarized, including the approximate thickness of zone(s). On this basis, several deep drill holes are recommended to verify whether there is considerable gold mineralization beneath the pyrrhotite anomaly zone(s).

Recent changes in forest structure and growth at the alpine‐treeline ecotone in the Rocky and Columbia Mountains of central British Columbia, Canada

AbstractAimGlobally, forests at the alpine‐treeline ecotone (ATE) are considered sensitive to warming temperatures; however, responses to recent climate change show high variability and many underlying processes remain unclear. This study aims to provide further insight into possible ATE forest responses to climate change by examining spatiotemporal patterns in recent tree regeneration and growth responses to climate across treeline forms.LocationThis study is situated at the ATE in the Rocky Mountain and Columbia Mountain ranges in central British Columbia, Canada.TaxonGymnosperms – subalpine fir (Abies lasiocarpa Hooker (Nutall)).MethodsWe collected tree and stand data from 48 plots across five study sites. Plots were distributed across three treeline stand types: (i) islands; (ii) abrupt; and (iii) fringes of regeneration adjacent to tree islands. We used a dendrochronological approach to analyse the ages of recently established trees in fringe stand types, detect long‐term trends in annual tree growth and quantify climate‐growth relationships.ResultsSeedling recruitment adjacent to tree islands occurred over a period of approximately 40 years (1960–2000), with two regeneration “pulses” in the late 1970s and 1980s. Abrupt and fringe trees showed a similar age structure and annual radial growth has increased in most trees over the past 30 years. Across the study region and stand types, summer temperature has the strongest influence on radial growth. Over the past 70 years, growth in tree islands has become increasingly correlated with growing season temperature variables.Main ConclusionsForest growth and structure have changed in coherent spatial and temporal patterns over recent decades at the ATE in central BC. Projections for sustained warming in this region will likely result in increased tree growth and potential continued expansion of forests into untreed areas below the treeline. These changes will have implications for hydrological regimes, wildlife habitat and carbon sequestration.

Small mammal responses to biosolids on grazed rangelands in British Columbia

Grasslands are globally declining due to habitat conversion, overgrazing, climate change, and changes in fire and drought regimes. Degraded grasslands are less able to support wildlife species, which contributes to the imperilment of many species. Biosolids are used by some ranchers as an organic amendment to support more plant growth and in turn more livestock. We worked on a large cattle ranch in central British Columbia, Canada, to determine how biosolids amendment affected small mammal populations, as mice and voles are major prey for many predators and contribute to seed dispersal and underground dynamics. We found that biosolids‐amended pastures had more grass cover and supported fewer deermice (Peromyscus maniculatus) than did unamended pastures. Voles were scarce, likely due to a cyclic low. Although we sampled sites that had had biosolids applied 1 or 3 years prior to our work started, deermouse populations were similarly low across these sites. The reduction in deermice on sites with biosolids relative to unamended sites could be a signal of habitat restoration, because deermice prefer disturbed habitats rather than ones with high plant cover. Grass cover was more than twice as high on sites amended with biosolids, making these sites less suitable for deermice.

Growth responses to thinning from below in uneven-aged interior Douglas-fir dominated stands

We assessed the impacts of three approaches to thinning from below with varying spatial patterns on several stand and individual tree variables for interior Douglas-fir ( Pseudotsuga menziesii var. glauca (Beissn.) Franco), interior spruce ( Picea glauca (Moench) Voss × Picea engelmannii Engelm.), and lodgepole pine ( Pinus contorta Dougl. Ex Loud. var. latifolia Englem.) in central British Columbia, Canada. The three thinning treatments were two experimental “clumped” treatments (3 m Clumped and 5 m Clumped) and the Standard (more uniform spacing) thinning treatment that was employed operationally at that time. We used long-term data from 24 plots measured five times over 21 years. Thinning increased stand basal area increment, with the plots that received the 5 m Clumped treatment having significantly higher periodic annual relative basal area increment than the unthinned Control plots. The responses for the two clumped treatments were not any lower than the Standard. The 3 m Clumped treatment was best if one is concerned about fast recovery of the growing space; however, the 5 m Clumped spacing treatment may be preferable if higher individual tree vigour is needed for resistance and resilience to fire, insects, and disease.

Awaruite, a New Large Nickel Resource: Flotation under Weakly Acidic Conditions

To support the transformation to clean low carbon technologies, there is a demand for critical metals such as nickel. Awaruite is a less common nickel-bearing mineral with unique properties and responses to mineral separation. This paper presents the findings of a flotation study to recover awaruite from the Baptiste ultramafic deposit, located in central British Columbia, Canada. Nickel recoveries of up to 65% at the rougher stage were obtained with xanthate as a collector at a pH level of 4.5. Awaruite flotation was shown to be highly dependent on the slurry pH. At weakly acidic conditions, the awaruite surface is activated through the dissolution of the passivation layer formed during grinding in alkaline conditions. Desliming was shown to reduce the acid consumption required to maintain the pH, probably by removing the highly reactive serpentine slimes generated during grinding. Rougher, followed by cleaner stages of flotation, showed that a high-grade concentrate can be produced with up to 45% nickel, 1.3% cobalt, 0.7% copper and negligible concentrations of penalty elements, such as arsenic, lead, and selenium, among others. A nickel flotation concentrate from an awaruite deposit is a promising feedstock for not only stainless-steel production but also for clean energy technologies.

Hydrothermal impacts of water release on early life stages of white sturgeon in the Nechako river, B.C. Canada

Water temperature plays a crucial role in the physiology of aquatic species, particularly in their survival and development. Thus, resource programs are commonly used to manage water quality conditions for endemic species. In a river system like the Nechako River system, central British Columbia, a water management program was established in the 1980s to alter water release in the summer months to prevent water temperatures from exceeding a 20 °C threshold downstream during the spawning season of Sockeye salmon (Oncorhynchus nerka). Such a management regime could have consequences for other resident species like the white sturgeon (Acipenser transmontanus). Here, we use a hydrothermal model and white sturgeon life stage-specific experimental thermal tolerance data to evaluate water releases and potential hydrothermal impacts based on the Nechako water management plan (1980–2019). Our analysis focused mainly on the warmest five-month period of the year (May to September), which includes the water release management period (July–August). Our results show that the thermal exposure risk, an index that measures temperature impact on species physiology of Nechako white sturgeon across all early life stages (embryo, yolk-sac larvae, larvae, and juvenile) has increased substantially, especially in the 2010s relative to the management program implementations’ first decade (the 1980s). The embryonic life stage was the most impacted, with a continuous increase in potential adverse thermal exposure in all months examined in the study. We also recorded major impacts of increased thermal exposure on the critical habitats necessary for Nechako white sturgeon recovery. Our study highlights the importance of a holistic management program with consideration for all species of the Nechako River system and the merit of possibly reviewing the current management plan, particularly with the current concerns about climate change impacts on the Nechako River.

Can Moisture-Indicating Understory Plants Be Used to Predict Survivorship of Large Lodgepole Pine Trees During Severe Outbreaks of Mountain Pine Beetle?

Abstract Why do some mature lodgepole pines survive mountain pine beetle outbreaks while most are killed? Here we test the hypothesis that mature trees growing in sites with vascular plant indicators of high relative soil moisture are more likely to survive mountain pine beetle outbreaks than mature trees associated with indicators of lower relative soil moisture. Working in the Clearwater Valley of south central British Columbia, we inventoried understory plants growing near large-diameter and small-diameter survivors and nonsurvivors of a mountain pine beetle outbreak in the mid-2000s. When key understory species were ranked according to their accepted soil moisture indicator value, a significant positive correlation was found between survivorship in large-diameter pine and inferred relative high soil moisture status—a finding consistent with the well-documented importance of soil moisture in the mobilization of defense compounds in lodgepole pine. We suggest that indicators of soil moisture may be useful in predicting the survival of large pine trees in future pine beetle outbreaks. Study Implications: A recent outbreak of the mountain pine beetle resulted in unprecedented levels of lodgepole pine mortality across southern inland British Columbia. Here, we use moisture-dependent understory plants to show that large lodgepole pine trees growing in sites with high relative moisture are more likely than similar trees in drier sites to survive severe outbreaks of mountain pine beetle—a finding that may be related to a superior ability to mobilize chemical defense compounds compared with drought-stressed trees.

Assessing the Surface Downward Longwave Irradiance Models Using ERA5 Input Data in Canada

Abstract Longwave radiation (LR) is one of the energy balance components responsible for warming and cooling water during hot summers. Both downward incoming LR, emitted by the atmosphere, and outgoing LR emitted by the land surface are not widely measured. The influence of clouds on the LR heat budget makes it even harder to establish reliable formulations for all-sky conditions. This paper uses air temperature and cloud cover from the ERA5 reanalysis database to compare 20 models for the downward longwave irradiance (DLI) at Earth’s surface and compare them with ERA5’s DLI product. Our work uses long-time continuous DLI measured data at three stations over Canada, and ERA5 reanalysis, a reliable source for data-scarce regions, such as central British Columbia (Canada). The results show the feasibility of the local calibration of different formulations using ERA5 reanalysis data for all-sky conditions with RMSE metrics ranging from 37.1 to 267.3 W m−2, which is comparable with ERA5 reanalysis data and can easily be applied at broader scales by implementing it into hydrological models. Moreover, it is shown that ERA5 gridded data for DLI shows the best results with RMSE = 31.7 W m−2. This higher performance suggests using ERA5 data directly as input data for hydrological and ecological models.

Stand- and tree-level responses to a range of initial basal area densities following partial harvest of complex spruce–fir stands in central British Columbia: 25-year results of a long-term field experiment

As forest managers increasingly seek to implement partial-harvest silviculture systems in complex forests, more data are required on the potential development of the residual stand following treatment. In this study, we present 25-year data from a long-term silvicultural study of tree- and stand-level responses to differing levels of basal area following partial harvest in a complex spruce–fir forest in central British Columbia, Canada. Reducing stand basal area elicited stronger basal area increment response in fir than spruce; however, spruce productivity was overall higher than fir across all treatments. Smaller trees increased their size proportionally more than larger trees, and thinning resulted in increased recruitment of smaller trees into larger diameter classes. At the stand-level, basal area reductions to well below 20 m2/ha resulted in higher volume and basal area growth over the length of this study, and suggest that optimum stand-level growth may be achieved at lower basal areas than suggested in prior literature. We also found a positive relationship between stand-level residual basal area and mortality. In central British Columbia, stand structure, species composition, and growth rates in complex spruce–fir forests can be maintained through partial-harvest silviculture treatments.

Meteorological Analysis of the Pacific Northwest June 2021 Heatwave

Abstract During the last week of June 2021, the Pacific Northwest region of North America experienced a record-breaking heatwave of historic proportions. All-time high temperature records were shattered, often by several degrees, across many locations, with Canada setting a new national record, the state of Washington setting a new record, and the state of Oregon tying its previous record. Here we diagnose key meteorology that contributed to this heatwave. The event was associated with a highly anomalous midtropospheric ridge, with peak 500-hPa geopotential height anomalies centered over central British Columbia. This ridge developed over several days as part of a large-scale wave train. Back trajectory analysis indicates that synoptic-scale subsidence and associated adiabatic warming played a key role in enhancing the magnitude of the heat to the south of the ridge peak, while diabatic heating was dominant closer to the ridge center. Easterly/offshore flow inhibited marine cooling and contributed additional downslope warming along the western portions of the region. A notable surface thermally induced trough was evident throughout the event over western Oregon and Washington. An eastward shift of the thermal trough, following the eastward migration of the 500-hPa ridge, allowed an inland surge of cooler marine air and dramatic 24-h cooling, especially along the western periphery of the region. Large-scale horizontal warm-air advection played a minimal role. When compared with past highly amplified ridges over the region, this event was characterized by much higher 500-hPa geopotential heights, a stronger thermal trough, and stronger offshore flow.

Terrestrial lichen caribou forage transplant success: year 5 and 6 results

The southern mountain caribou—a subpopulation of caribou found in British Columbia—is listed on Schedule 1 of the Federal Species at Risk Act as Threatened. Woodland caribou are diet specialists, relying on Cladonia subgenus Cladina lichen as a primary food source during winter months. Lichens are burned along with trees and other vegetation during stand‐replacing wildfire events, a natural disturbance in caribou ranges. In an attempt to accelerate the return of post‐fire forests to productive caribou winter terrestrial lichen habitat, this study examined the survival and cover of three species of transplanted lichens in a post‐wildfire environment in north central British Columbia, Canada, both with and without forest litter amendments. Chlorophyll fluorescence was used to evaluate lichen survival by measuring potential photosynthetic activity. The results of this study demonstrate that transplanted fragments and mats of Cladonia subgenus Cladina had survived 5 and 6 years after being transplanted within a post‐wildfire environment, and had significantly greater percent cover when compared to the controls. The Fv/Fm results indicated that transplanted lichens survived, regardless of species, propagule type, or whether amendments were applied.

Landscape disturbance alters the composition and diversity of the diet of moose, a generalist herbivore

Human-caused landscape disturbance is one of the major threats to large herbivores, globally. Across central British Columbia (BC), Canada, industrial forest harvesting has resulted in rapid change to forest structure and composition. Concurrent with the increase in forest harvesting, moose (Alces alces) populations across central BC have declined, some dramatically. We studied moose diet across three seasons in two regional study areas that represented a range of logging intensity and rate of apparent starvation of moose. We used microhistological analysis of pellets to identify the proportional consumption of major plant groups that were known forage for moose across the study areas, as well as the diversity of the diet of moose. We used regression models to test whether the composition and diversity of moose diet in two study areas were consistent with the Niche Expansion Hypothesis or the Niche Shrinkage Hypothesis. In areas of increased density and size of clearcuts, moose consumed fewer shrubs and fir trees and their diet was more diverse. Where application of herbicides was common, moose consumed fewer forbs and their diet was more diverse. Both responses were consistent with the Niche Expansion Hypothesis. In areas of increased disturbance by wildfire, moose consumed less fir and more shrubs. Our results suggest that landscape disturbance in the form of extensive and rapid forest harvesting can influence the composition and diversity of the diet of moose.

Raptors benefit from biosolids applications on rangelands

Globally, many grasslands have been lost or degraded via settlement, conversion to agriculture, or use as pasture. These losses have damaged the ability of migratory and nomadic birds of prey to find suitable breeding territories. Habitat restoration of degraded grasslands via the application of biosolids, the treated and sterilized remains from sewage treatment plants, improves soil water retention and nutrient profile, leading to substantial gains in plant growth and nutritive quality. Gains to wild and domestic herbivores have been documented, but impacts to predators are poorly known. Here, we test the hypothesis that biosolids-applied pastures are attractive to and support migratory and nomadic avian predators in central British Columbia, Canada. We obtained habitat records from sightings and prey remains from pellets for three vole-specialists, Long-eared Owls (<em>Asio otus</em>), Short-eared Owls (<em>A. flammeus</em>), and Northern Harriers (<em>Circus hudsonius</em>), as well as the generalist American Kestrels (<em>Falco sparverius</em>). During 5 years, the three diurnal species preferentially used biosolids-applied pastures, and kestrels and owls nested in biosolids-applied pastures or in forest patches adjacent to these pastures. Grasshoppers were more abundant on pastures with biosolids and were common prey for American Kestrels. The owls and harriers preferentially consumed voles, although Short-eared Owls consumed deermice (<em>Peromyscus maniculatus</em>) as a major additional food source during years when voles were scarce. Long-eared Owls were documented only in the 2 years when voles were common. Collectively, these results suggest that biosolids-amended landscapes may attract raptors, even when vole densities are low.

The early Eocene flora of Horsefly, British Columbia, Canada and its phytogeographic significance

About forty species, including a bryophyte, ferns, conifers, Ginkgo, and over 35 angiosperms, are recognized based on compression-impression remains from the early Eocene of Horsefly, British Colombia, Canada. This flora is in the north central part of a chain of late early Eocene fossil assemblages known as floras of the “Okanagan Highlands” (= “Okanogan Highlands” in the US). These floras extend from north central British Columbia, Canada southeast to Republic, Washington, USA. The Horsefly flora shows similarities to other Eocene Okanagan Highlands floras, such as McAbee, Falkland, Thomas Ranch and Republic, but with some additional rare taxa. In the broader sense, the Horsefly flora can be compared with early and middle Eocene floras of eastern Asia and midcontinental North America, but shares fewer elements with Europe. Ginkgo, Metasequoia, Pinus, Palaeocarpinus, ulmaceous leaves and Deviacer are shared with northeastern China as well as western North American sites. Fagopsis, Macginitiea, Dipteronia, Florissantia, Sassafras and Lagokarpos also occur in other western North American Eocene floras and Koelreuteria and Jenkinsella with Eocene paleofloras of China. These comparisons demonstrate probable floristic exchange between northwestern North America and northeastern China via a Beringian route during the late early Eocene.

Geographic variability of hybridization between red-breasted and red-naped sapsuckers.

Hybrid zones reveal the strength of reproductive isolation between populations undergoing speciation and are a key tool in evolutionary biology research. Multiple replicate transects across the same hybrid zone offer insight into the dynamics of hybridization in different environments, clarifying the role of extrinsic forces on the speciation process. Red-breasted and red-naped sapsuckers (Sphyrapicus ruber and Sphyrapicus nuchalis) have a long zone of contact over approximately 1,600 km from central British Columbia, Canada to central California, USA. We used Genotyping-by-Sequencing data from three independent sapsucker hybrid zone transects to compare hybridization dynamics between these species under variable geoclimatic conditions. We generated geographic clines of the genomic data to compare hybrid zone widths and used random forests models and linear regression to assess the relationship between climate and sapsucker ancestry along each transect. Our results show variation in the directionality of backcrossing, often indicative of moving hybrid zones. We note variable cline widths among transects, indicating differences in selection maintaining hybrid zone dynamics. Furthermore, random forests models identified different variables in close association with sapsucker ancestry across each transect. These results indicate a lack of repeatability across replicate transects and a strong influence of the local environment on hybrid zone dynamics.